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If you’re upgrading your Service Provider network from ATM- or SDH-based core to Carrier Ethernet core, you could be tempted to keep the unnumbered point-to-point links. The practice of using unnumbered P2P links is debatable, but if you want to, you can configure them on VLAN interfaces in recent IOS releases.

Huh, just though of that, would be interesting to see how CEF adjacencies are created over those unnumbered links. Proxy ARP? I'll try to lab this one ASAP.

There are "point-to-point" VLANs, i.e. VLANs with no MAC address learning enabled, which works pretty much like P2P logical circuits (or hubs :). Thos are not the EVCs, but simple VLANs with no MAC address learning.

Wonder if one can instruct CEF layer to simply push the VLAN header instead of "gleaning" for the destination MAC when switching packets over the unnumbered P2P subinterface.

Yeah, but theoretically you may use broadcast destination as it should not matter on the P2P link (provided that the Ethernet transport is configured properly). Would actually save time on ARPing and resolving the "glean" adjacencies.

The author

Ivan Pepelnjak (CCIE#1354 Emeritus), Independent Network Architect at ipSpace.net, has been designing and implementing large-scale data communications networks as well as teaching and writing books about advanced internetworking technologies since 1990.